Gear oil in the differentials on a shaftie

[Kratzer]

Wow, I just changed the molasses in the gearboxes with some fresh oil, and the difference is unbelievable. Such smoother acceleration and it seesm like the bike coasts a lot longer. Not sure if that is feasible, but it sure seems like it.

All you G owners- stop procrastinating. Its worth the 20 minutes an d10 bucks it takes.

[emjay]

It sure does make a big difference. Definitely high on the must do list when you first get one of these old GSs. And of course part of the regular maitenance schedule.

[doctorgonzo]

Mine says it uses sae 90 I think. What type did you use?

[Kratzer]

Fully synthetic 75 w90

It said on the back "for use is hypoid applications" as well.

[doctorgonzo]

I searched and found BassCliffs guide, with pictures, and he's using the 75-90 synthetic as well. I'm going to do it this weekend. I thought about waiting for my machined screws to arrive so I could replace them while I'm at it, but probably just do that when they arrive in a week or so. That cover isn't that hard to pull for fastener replacement.

[BassCliff]

Hi,

If you really want to do a complete job, you can also replace the crush washers on the fill/drain plugs of the bevel gear case and final drive unit. There should be part numbers in one of those guides. I haven't changed mine yet but they'll certainly get changed if I see a leak.

Thank you for your indulgence,

BassCliff

[lurch12_2000]

One of the first things I did when I got my bike last year was to change the gear oil (80w90) in both my gear box and the differential. Oil wasn't that bad but seemed to shift smoother. I normally take it for at least a 10 mile run to heat up the gear oil so it flows more like water and drains better. Do not overfill.

[emjay]

... Do not overfill.

You can't really overfill the differential if you add the oil with the diff attached to the bike. If you pour too much in it just comes back out. They design it that way on purpose. You don't have to measure, just add oil till it reaches the opening.

[lurch12_2000]

You can't really overfill the differential if you add the oil with the diff attached to the bike. If you pour too much in it just comes back out. They design it that way on purpose. You don't have to measure, just add oil till it reaches the opening.

I would disagree, as gear oil heats it expands and you should recheck the level so that it doesn't block the vent.
The other thing is when you're squirting the new oil in it may not settle right away so if you put the fill plug back on too quickly, you may not get an accurate read. Just my opinion.